A critical question for guideline developers, clinical trialists, clinicians, patients, and policy makers is whether the population enrolled in RCTs is representative of the patients seen in primary care. Allergic rhinitis guidelines such as those established by Allergic Rhinitis and its Impact on Asthma (ARIA), have been available for many years and are due for a revision.

This cohort study was conducted to assess the percentage of patients with allergic rhinitis cared for in primary care that would have been eligible for inclusion in RCTs to inform the level of directness of the evidence5 between the population under study and the typical population being cared for in primary practice. The study included 311 consecutive patients with allergic rhinitis cared for by 48 GPs in the Languedoc-Roussillon region of France within 2 weeks during the grass pollen season. The characteristics of these patients were compared with those of patients included in the 4 largest placebo-controlled RCTs of persistent and intermittent allergic rhinitis.

The researchers found that only 7.4% (95% CI, 4.5% to 10.3%) of these patients would have been enrolled in the RCTs; the primary reasons for this difference were as follows:

• Diagnosis of allergy based on skin test results; serum specific IgE levels, or both (20.4%)

• Severity of allergic rhinitis (11.5%)

• Other chronic diseases (11.4%)

• History of sinusitis (10.4%)

• Asthma comorbidity (10.1%)

A sensitivity analysis excluding contraception and the diagnosis of allergy showed that the percentage of representative patients increased to 20.2% (95% CI, 15.8% to 24.7%).

The researchers conclude from these findings that only a small proportion of patients with allergic rhinitis seen in the primary care setting for allergic rhinitis would be eligible for RCTs. They note that although the non-representativeness of clinical trial populations is common knowledge, the data presented in this study quantify the huge magnitude of the differences between clinical trial participants and the general population. This is of concern as patients consulting with clear-cut symptoms during a defined allergen exposure might be treated according to guidelines developed from data in RCTs. They advise that guideline developers and health decision makers need to make careful judgments about the directness of the evidence from RCTs conducted in highly controlled settings.